Anthrax Epidemiology
The incidence and distribution in Montana and elsewhere, along with the information regarding the spread of the disease.
Anthrax has an almost worldwide distribution and is a zoonotic disease, meaning it may spread from animals to humans. All mammals appear to be susceptible to anthrax to some degree, but ruminants such as cattle, sheep, and goats are the most susceptible and commonly affected, followed by horses, and then swine.
Incidence in Montana*
There were two cases of anthrax diagnosed in cattle in Montana in September 2005, both in Roosevelt County. The first case was on tribal land northwest of Culbertson. A total of 39 cattle died and were appropriately buried. Although the premises of the second case was also near Culbertson, it was not adjacent to where the first case was confirmed. Four cattle died and were appropriately buried as a result of the second anthrax case.
There were two cases of anthrax diagnosed in cattle in Montana in the summer of 1999, one in May and one in August. The two incidents were unrelated, having occurred far apart from each other in isolated parts of eastern Montana. Both cases were contained early and led to no additional problems.
Prior to 1999, the last case of naturally occurring anthrax in Montana was reported in 1985. The organism naturally occurs in the soil in many parts of Montana, as well as other states.
Incidence in the United States and World
Anthrax is endemic to the United States and most other countries of the world, occurring sporadically as environmental conditions allow. Reports of the disease come from other countries that have the necessary environmental conditions and the veterinary infrastructure to be aware of the disease.
Source: APHIS - http://www.aphis.usda.gov
Spread of Anthrax(Transmission)
The anthrax organism may be spread within an area by streams, insects, wild animals and birds, and contamination from wastes of infected animals. Anthrax may be perpetuated in nature by hosts such as a wildlife reservoir, which in turn spills over into the livestock population. Animals are usually infected by ingesting soilborne spores, such as in contaminated food or water. Spores can be picked up directly from the soil through grazing or from feed grown on infected soil. When periods of drought cause livestock to forage much closer to the ground, animals may ingest spores in soil they accidentally eat along with forage. After flooding, the concentration of spores caught in standing water increases when pre-existing or transitory ponds begin to evaporate. Spores may also be present in bonemeal, protein concentrates, excreta, and tissue and body fluids of infected carcasses.